# Drought Treated Seedlings of Quercus petraea (Matt.) Liebl., Q. robur L. and Their Morphological Intermediates Show Differential Radial Growth and Wood Anatomical Traits

^{1}

^{2}

^{3}

^{4}

^{5}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Source Material and Experimental Design

^{3}powdered compound fertilizer NPK 12 + 14 + 24).

#### 2.2. Plant Measurements and Preparation of the Microsectioning

#### 2.3. Wood Anatomical Traits

#### 2.4. Data Analysis

_{T}.T + β

_{W}.W + β

_{H}.H + β

_{TW}.T.W + β

_{TH}.T.H + β

_{WH}.W.H

_{T}.T + β

_{H}.H + β

_{TH}.T.H

_{T}.T + β

_{W}.W + β

_{H}.H + β

_{TW}.T.W + β

_{TH}.T.H + β

_{WH}.W.H + plantID (random)

_{T}.T + β

_{W}.W + β

_{H}.H + β

_{TW}.T.W + β

_{TH}.T.H + β

_{WH}.W.H

_{tr}− β

_{T}.T − β

_{W}.W − β

_{RGR}.RGR − β

_{TW}.T.W − β

_{TRGR}.T.RGR − β

_{WRGR}.W.RGR

_{tr}is the threshold value indicating an intercept for each transition from one level of the ordinal response variable to the next. Models were reduced up to only significant explanatory variables using the command drop1.

## 3. Results

#### 3.1. Pith Radius

#### 3.2. Radial Growth of the Secondary Xylem in the First Three Growing Seasons

_{pr}with p-value of 0.004 in Table 2).

_{rp}with p-value = 0.007 in Table 2). Seedlings from Q. robur developed significantly larger ring widths than seedlings from Q. petraea (p-value < 0.001 for T

_{r}in Table 2). This difference attenuated in seedlings with a higher relative growth rate (significant interaction term between T

_{r}and RGR

_{2016}with p-value = 0.011). Additionally, the ring width in seedlings from Q. robur differed from seedlings from Q. petraea depending on the relative growth rate in height (significant interaction term between T

_{r}and the relative height growth with p-value = 0.011 in Table 2). For a given adjusted relative extractable water value in Figure 3c, the distance between the full and dashed lines for seedlings from Q. robur is smaller than the distances between these two lines for the three other taxa, suggesting that the ring width in seedlings from Q. robur is less influenced by the relative growth rate in height in comparison with Q. petraea.

#### 3.3. Latewood Vessel Diameter

_{r}) with p-value = 0.004 in 2015 and p-value = 0.006 in 2016 in Table 3), which was opposite to the first growing season.

#### 3.4. Formation of Intra-Annual Density Fluctuations in the Xylem Growth Zone

#### 3.5. Dendritic Vessel Pattern

_{pr}, T

_{r}and T

_{rp}with p-values = 0.012, 0.002 and 0.003, respectively, in Table 6, Figure 6a).

_{rp}with p-value of 0.007 and significant interaction term between T

_{rp}and W with p-value = 0.006 in Table 6).

#### 3.6. Level of Earlywood Vessel Ring Closure

_{2015}, with a p-value < 0.001 in Table 7) (dashed lines showing higher probabilities than the corresponding full lines for a given adjusted relative extractable water in 2014 in Figure 7a). Seedlings from Q. robur and from the short stalked intermediate differed significantly from the seedlings from Q. petraea and from the long-stalked intermediates (p-values < 0.001 for both T

_{r}and T

_{rp}, Table 7). This indicated that for a given percentage of vessel ring closure, seedlings from Q. petraea and from the long stalked intermediate tended to a lower probability of having achieved this percentage in comparison to seedlings from Q. robur and from the short stalked intermediate, or in other words, seedlings from Q. petraea and from the long stalked intermediate displayed less ring closure when compared with seedlings from Q. robur and the short stalked intermediate independent from the drought treatment in 2014.

## 4. Discussion

#### 4.1. Differentiation Between Offspring From Q. Robur, Q. Petraea and the Morphological Intermediates

#### 4.2. Drought Responses

## 5. Conclusions

## Supplementary Materials

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

- Cornelissen, J.H.C.; Diez, P.C.; Hunt, R. Seedling growth, allocation and leaf attributes in a wide range of woody plant species and types. J. Ecol.
**1996**, 84, 755–765. [Google Scholar] [CrossRef] - Lindner, M.; Fitzgerald, J.B.; Zimmermann, N.E.; Reyer, C.; Delzon, S.; van der Maaten, E.; Schelhaas, M.J.; Lasch, P.; Eggers, J.; van der Maaten-Theunissen, M.; et al. Climate change and European forests: What do we know, what are the uncertainties, and what are the implications for forest management? J. Environ. Manag.
**2014**, 146, 69–83. [Google Scholar] [CrossRef] [PubMed] [Green Version] - Hopkins, W.; Huner, N. Introduction to Plant Physiology; Wiley: Hoboken, NJ, USA, 2008. [Google Scholar]
- Sperry, J.S. Evolution of water transport and xylem structure. Int. J. Plant. Sci.
**2003**, 164, S115–S127. [Google Scholar] [CrossRef] [Green Version] - Sass-Klaassen, U.; Sabajo, C.R.; den Ouden, J. Vessel formation in relation to leaf phenology in pedunculate oak and European ash. Dendrochronologia
**2011**, 29, 171–175. [Google Scholar] [CrossRef] - Kitin, P.; Funada, R. Earlywood vessels in ring-porous trees become functional for water transport after bud burst and before the maturation of the current-year leaves. IAWA J.
**2016**, 37, 315–331. [Google Scholar] [CrossRef] - Hros, M.; Vavrcik, H. Comparison of earlywood vessel variables in the wood of Quercus. robur. L. and Quercus. petraea. (mattuschka) Liebl. Growing at the same site. Dendrochronologia
**2014**, 32, 284–289. [Google Scholar] [CrossRef] - Choat, B.; Jansen, S.; Brodribb, T.J.; Cochard, H.; Delzon, S.; Bhaskar, R.; Bucci, S.J.; Feild, T.S.; Gleason, S.M.; Hacke, U.G.; et al. Global convergence in the vulnerability of forests to drought. Nature
**2012**, 491, 752. [Google Scholar] [CrossRef] [Green Version] - Tyree, M.T.; Cochard, H. Summer and winter embolism in oak: Impact on water relations. Ann. Sci. Forest
**1996**, 53, 173–180. [Google Scholar] [CrossRef] [Green Version] - Levanic, T.; Cater, M.; McDowell, N.G. Associations between growth, wood anatomy, carbon isotope discrimination and mortality in a Quercus. robur. forest. Tree Physiol.
**2011**, 31, 298–308. [Google Scholar] [CrossRef] [Green Version] - Ellmore, G.S.; Ewers, F.W. Hydraulic conductivity in trunk xylem of elm, Ulmus americana. IAWA Bull.
**1985**, 6, 303–307. [Google Scholar] [CrossRef] - Cochard, H.; Tyree, M.T. Xylem dysfunction in Quercus.-vessel sizes, tyloses, cavitation and seasonal-changes in embolism. Tree Physiol.
**1990**, 6, 393–407. [Google Scholar] [CrossRef] [PubMed] [Green Version] - Govaerts, R.; Frodin, D.G. World Checklist and Bibliography of Fagales (Betulaceae, Corylaceae, Fagaceae and Ticodendraceae); Royal Botanic Gardens: Kew, UK, 1998. [Google Scholar]
- Nixon, K.C. Ecology and conservation of neotropical montane oak forests. In Ecology and Conservation of Neotropical Montane Oak Forests; Kappelle, M., Ed.; Springer: Berlin/Heidelberg, Germany, 2006; Volume 185. [Google Scholar]
- Grosser, D. Die Hölzer Mitteleuropas; Springer: Berlin/Heidelberg, Germany, 1977. [Google Scholar]
- Bacilieri, R.; Ducousso, A.; Petit, R.J.; Kremer, A. Mating system and asymmetric hybridization in a mixed stand of European oaks. Evolution
**1996**, 50, 900–908. [Google Scholar] [CrossRef] [PubMed] - Lepais, O.; Petit, R.; Guichoux, E.; Lavabre, J.; Alberto, F.; Kremer, A.; Gerber, S. Species relative abundance and direction of introgression in oaks. Mol. Ecol.
**2009**, 18, 2228–2242. [Google Scholar] [CrossRef] [PubMed] - Petit, R.J.; Bodenes, C.; Ducousso, A.; Roussel, G.; Kremer, A. Hybridization as a mechanism of invasion in oaks. New Phytol.
**2004**, 161, 151–164. [Google Scholar] [CrossRef] [Green Version] - Barigah, T.S.; Charrier, O.; Douris, M.; Bonhomme, M.; Herbette, S.; Améglio, T.; Fichot, R.; Brignolas, F.; Cochard, H. Water stress-induced xylem hydraulic failure is a causal factor of tree mortality in beech and poplar. Ann. Bot.
**2013**, 112, 1431–1437. [Google Scholar] [CrossRef] [PubMed] - Kuster, T.M.; Bleuler, P.; Arend, M.; Günthardt-Goerg, M.S.; Schulin, R. Soil water, temperature regime and growth of young oak stands grown in lysimeters subjected to drought stress and air warming. Bull. BGS
**2011**, 32, 7–12. [Google Scholar] - Thomas, F.M. Growth and water relations of four deciduous tree species (Fagus. sylvatica. L., Quercus. petraea. [matt.] liebl., Q. pubescens willd., Sorbus aria [L.] cr.) occurring at central-European tree-line sites on shallow calcareous soils: Physiological reactions of seedlings to severe drought. Flora
**2000**, 195, 104–115. [Google Scholar] - Kleinschmit, J.R.G.; Bacilieri, R.; Kremer, A.; Roloff, A. Comparison of morphological and genetic traits of pedunculate oak (Q. robur L) and sessile oak (Q. petraea (Matt.) Liebl.). Silvae Genet.
**1995**, 44, 256–269. [Google Scholar] - Feuillat, F.; Dupouey, J.L.; Sciama, D.; Keller, R. A new attempt at discrimination between Quercus petraea and Quercus robur based on wood anatomy. Can. J. Forest Res.
**1997**, 27, 343–351. [Google Scholar] [CrossRef] - Fonti, P.; Heller, O.; Cherubini, P.; Rigling, A.; Arend, M. Wood anatomical responses of oak saplings exposed to air warming and soil drought. Plant. Biol.
**2013**, 15, 210–219. [Google Scholar] [CrossRef] - Garcia-Gonzalez, I.; Souto-Herrero, M.; Campelo, F. Ring-porosity and earlywood vessels: A review on extracting environmental information through time. IAWA J.
**2016**, 37, 295–314. [Google Scholar] [CrossRef] - Gieger, T.; Thomas, F.M. Effects of defoliation and drought stress on biomass partitioning and water relations of Quercus robur and Quercus petraea. Basic. Appl. Ecol.
**2002**, 3, 171–181. [Google Scholar] [CrossRef] - Mayer, H. Waldbau auf Soziologisch-Ökologischer Grundlage; Gustav Fischer Verlag-Stuttgart: New York, NY, USA, 1977; p. 483. [Google Scholar]
- Kuster, T.M.; Arend, M.; Gunthardt-Goerg, M.S.; Schulin, R. Root growth of different oak provenances in two soils under drought stress and air warming conditions. Plant Soil.
**2013**, 369, 61–71. [Google Scholar] [CrossRef] [Green Version] - Turcsán, A.; Steppe, K.; Sárközi, E.; Erdélyi, É.; Missoorten, M.; Mees, G.; Mijnsbrugge, K.V. Early summer drought stress during the first growing year stimulates extra shoot growth in oak seedlings (Quercus petraea). Front. Plant Sci.
**2016**, 7, 193. [Google Scholar] [CrossRef] [Green Version] - Vander Mijnsbrugge, K.; Turcsán, A.; Maes, J.; Duchêne, N.; Meeus, S.; Steppe, K.; Steenackers, M. Repeated summer drought and re-watering during the first growing year of oak (Quercus petraea) delay autumn senescence and bud burst in the following spring. Front. Plant Sci.
**2016**, 7, 419. [Google Scholar] [CrossRef] - Arend, M.; Kuster, T.; Gunthardt-Goerg, M.S.; Dobbertin, M. Provenance-specific growth responses to drought and air warming in three European oak species (Quercus robur, Q. petraea. and Q. pubescens). Tree Physiol.
**2011**, 31, 287–297. [Google Scholar] [CrossRef] [Green Version] - Vander Mijnsbrugge, K.; Turcsan, A.; Maes, J.; Duchene, N.; Meeus, S.; Van der Aa, B.; Steppe, K.; Steenackers, M. Taxon-independent and taxon-dependent responses to drought in seedlings from Quercus robur L., Q. petraea (Matt.) Liebl. and their morphological intermediates. Forests
**2017**, 8, 407. [Google Scholar] [CrossRef] [Green Version] - Vander Mijnsbrugge, K.; Coart, E.; Beeckman, H.; Van Slycken, J. Conservation measures for autochthonous oaks in flanders. Forest Genet.
**2003**, 10, 207–217. [Google Scholar] - Vander Mijnsbrugge, K.; Cox, K.; Van Slycken, J. Conservation approaches for autochthonous woody plants in flanders. Silvae Genet.
**2005**, 54, 197–206. [Google Scholar] [CrossRef] [Green Version] - Vander Mijnsbrugge, K.; De Cleene, L.; Beeckman, H. A combination of fruit and leaf morphology enables taxonomic classification of the complex Q. robur L.-Q. X rosacea bechst-Q. petraea (Matt.) Liebl. In autochthonous stands in flanders. Silvae Genet.
**2011**, 60, 139–148. [Google Scholar] [CrossRef] [Green Version] - Rueden, C.; Dietz, C.; Horn, M.; Schindelin, J.; Northan, B.; Berthold, M.; Eliceiri, K. Imagej Ops [Software]. Available online: https://imagej.Net/ops (accessed on 1 January 2020).
- Anonymous. IAWA list of microscopic features for hardwood identification-with an appendix on non-anatomical information. IAWA Bull.
**1989**, 10, 219. [Google Scholar] - Bates, D.; Machler, M.; Bolker, B.M.; Walker, S.C. Fitting linear mixed-effects models using lme4. J. Stat. Softw.
**2015**, 67, 1–48. [Google Scholar] [CrossRef] - Christensen, R.H.B. Ordinal: Regression Models for Ordinal Data. R Package Version 2013.10-31. 2013. Available online: https://cran.r-project.org/web/packages/ordinal/ (accessed on 1 January 2020).
- Priya, P.B.; Bhat, K.M. False ring formation in teak (Tectona grandis Lf) and the influence of environmental factors. Forest Ecol. Manag.
**1998**, 108, 215–222. [Google Scholar] [CrossRef] - Leal, S.; Melvin, T.M.; Grabner, M.; Wimmer, R.; Briffa, K.R. Tree-ring growth variability in the austrian alps: The influence of site, altitude, tree species and climate. Boreas
**2007**, 36, 426–440. [Google Scholar] [CrossRef] - Hasenauer, H.; Nemani, R.R.; Schadauer, K.; Running, S.W. Climate variations and tree growth between 1961 and 1995 in Austria. Eur. Forest Inst. Proc.
**1999**, 27, 75–86. [Google Scholar] - Pretzsch, H.; Biber, P.; Schutze, G.; Uhl, E.; Rotzer, T. Forest stand growth dynamics in central Europe have accelerated since 1870. Nat. Commun.
**2014**, 5, 1–10. [Google Scholar] [CrossRef] [Green Version] - Heuret, P. Ecologie, Développement Architectural et Évolution de la Tribu des Cecropieae; Mémoire de HDR (GAIA): Montpellier, France, 2019. [Google Scholar]
- Alberto, F.J.; Aitken, S.N.; Alia, R.; Gonzalez-Martinez, S.C.; Hanninen, H.; Kremer, A.; Lefevre, F.; Lenormand, T.; Yeaman, S.; Whetten, R.; et al. Potential for evolutionary responses to climate change-evidence from tree populations. Glob. Chang. Biol.
**2013**, 19, 1645–1661. [Google Scholar] [CrossRef] [Green Version] - Hajek, P.; Kurjak, D.; von Wuhlisch, G.; Delzon, S.; Schuldt, B. Intraspecific variation in wood anatomical, hydraulic, and foliar traits in ten European beech provenances differing in growth yield. Front. Plant Sci.
**2016**, 7, 791. [Google Scholar] [CrossRef] [Green Version] - Levy, G.; Becker, M.; Duhamel, D. A comparison of the ecology of pedunculate and sessile oaks-radial growth in the center and northwest of france. For. Ecol. Manag.
**1992**, 55, 51–63. [Google Scholar] [CrossRef] - Cochard, H.; Breda, N.; Granier, A.; Aussenac, G. Vulnerability to air-embolism of 3 European oak species (Quercus petraea (Matt.) Liebl., Quercus pubescens willd., Quercus robur L.). Ann. Sci. For.
**1992**, 49, 225–233. [Google Scholar] [CrossRef] [Green Version] - Büsgen, M.; Münch, E.; Thomson, T. The Structure and Life of Forest Trees; Chapman and Hall: London, UK, 1929. [Google Scholar]
- Gonzalez-Gonzalez, B.D.; Vazquez-Ruiz, R.A.; Garcia-Gonzalez, I. Effects of climate on earlywood vessel formation of Quercus robur and Q. pyrenaica at a site in the northwestern Iberian peninsula. Can. J. Forest Res.
**2015**, 45, 698–709. [Google Scholar] [CrossRef] - De Micco, V.; Campelo, F.; De Luis, M.; Brauning, A.; Grabner, M.; Battipaglia, G.; Cherubini, P. Intra-annual density fluctuations in tree rings: How, when, where, and why? IAWA J.
**2016**, 37, 232–259. [Google Scholar] [CrossRef] - Die, A.; Kitin, P.; Kouame, F.N.; Van den Bulcke, J.; Van Acker, J.; Beeckman, H. Fluctuations of cambial activity in relation to precipitation result in annual rings and intra-annual growth zones of xylem and phloem in teak (Tectona grandis) in Ivory Coast. Ann. Bot. Lond.
**2012**, 110, 861–873. [Google Scholar] [CrossRef] [PubMed] [Green Version] - Campelo, F.; Gutierrez, E.; Ribas, M.; Nabais, C.; Freitas, H. Relationships between climate and double rings in Quercus ilex from northeast Spain. Can. J. Forest Res.
**2007**, 37, 1915–1923. [Google Scholar] [CrossRef] - Copenheaver, C.A.; Gartner, H.; Schafer, I.; Vaccari, F.P.; Cherubini, P. Drought-triggered false ring formation in a mediterranean shrub. Botany
**2010**, 88, 545–555. [Google Scholar] [CrossRef] - Pflug, E.E.; Buchmann, N.; Siegwolf, R.T.W.; Schaub, M.; Rigling, A.; Arend, M. Resilient leaf physiological response of European beech (Fagus sylvatica L.) to summer drought and drought release. Front. Plant Sci.
**2018**, 9, 187. [Google Scholar] [CrossRef] [Green Version]

**Figure 1.**Cross sections of oak seedlings: (

**a**) intra-annual density fluctuation (arrow n° 1) in the secondary xylem of the first growing season. Arrow n° 2 indicates the year ring border between the first and the second growing season. (

**b**) Cross section indicating a dendritic pattern of latewood vessels in the second growing season (long arrow) and a 50% of vessel ring closure at the onset of the earlywood in the second growing season (short arrows).

**Figure 2.**Modelled pith radius depending on the height the seedlings attained in the first growing season and on the taxon of the mother tree. p: Q. petraea, pr: long stalked intermediate, r: Q. robur, rp: short-stalked intermediate.

**Figure 3.**Modelled ring widths in the first three growing seasons (2014, 2015 and 2016), depending on the height of the seedlings in 2014 or on the relative growth rate in height (2015 and 2016), on the taxon of the mother trees and, only for 2015 and 2016, on the adjusted relative extractable water in 2014. p: Q. petraea, pr: long stalked intermediate, r: Q. robur, rp: short-stalked intermediate: (

**a**) first growing season 2014; (

**b**) second growing season 2015; (

**c**) third growing season 2016.

**Figure 4.**Modelled vessel diameter depending on the height of the seedlings (2014) or on the relative growth rate in height (2015), on the adjusted relative extractable water in 2014 (latewood vessel diameters in rings of 2015 and 2016) and on the taxon of the mother trees (latewood vessel diameters in rings of 2014, 2015 and 2016): (

**a**) first growing season 2014; (

**b**) second growing season 2015; (

**c**) third growing season 2016. p: Q. petraea, pr: long stalked intermediate form, r: Q. robur, rp: short-stalked intermediate form.

**Figure 5.**Modelled probability of having formed an intra-annual density fluctuation in the secondary xylem in 2014, depending on the adjusted relative extractable water in 2014.

**Figure 6.**Modelled probability of having formed dendritic patterns (grouped vessels in flame-like structures) in the latewood xylem, depending on the relative growth rate in height, on the taxon of the mother tree and, only for 2016, on the adjusted relative extractable water in 2014: (

**a**) second growing season 2015; (

**b**) third growing season 2016. p: Q. petraea, pr: long stalked intermediate form, r: Q. robur, rp: short-stalked intermediate form.

**Figure 7.**Modelled probabilities for a given level of vessel ring closure at the onset of the earlywood in the second and the third growing season, depending on the taxon of the mother tree and, only for 2015, on the adjusted relative extractable water in 2014 and on the relative growth rate in height in 2015: (

**a**) probabilities for having formed 30%, 40%, 50% or 60% of the vessel ring in the second growing season 2015; (

**b**) probabilities for having formed 30%, 40%, 50% or 60% of the vessel ring in the third growing season 2016. p: Q. petraea, pr: long stalked intermediate form, r: Q. robur, rp: short-stalked intermediate form.

**Table 1.**Number of oak seedlings (n) according to the drought treatment in 2014 and the taxon of the mother tree.

Treatment | Taxon Mother Tree * | n |
---|---|---|

control | p | 42 |

pr | 10 | |

r | 35 | |

rp | 27 | |

drought | p | 30 |

pr | 10 | |

r | 27 | |

rp | 29 |

*****p: Quercus petraea, pr: long stalked intermediate, r: Q. robur, rp: short stalked intermediate.

**Table 2.**Model statistics for the response variables pith radius and ring widths in 2014, 2015 and 2016. The standard level of the categorical variable taxon of the mother tree (T) was Q. petraea, to which the other taxa were compared with. T

_{pr}: long stalked intermediate form, T

_{r}: Q. robur, T

_{rp}: short-stalked intermediate form. H

_{2014}: height at the end of the first growing season. RGR

_{2015}and RGR

_{2016}: relative growth rates in height for 2015 and 2016, respectively. W: adjusted relative extractable water in 2014.

Pith | Ring 2014 | ||||||||
---|---|---|---|---|---|---|---|---|---|

Estimate | Std. Error | T-Value | p-Value | Estimate | Std. Error | T-Value | p-Value | ||

(Intercept) | 258.8 | 26.5 | 9.77 | <0.001 *** | (Intercept) | 290.3 | 68.0 | 4.26 | <0.001 *** |

T_{pr} | 55.2 | 57.1 | 0.97 | 0.335 | T_{pr} | −28.6 | 146.7 | −0.20 | 0.846 |

T_{r} | 87.9 | 32.5 | 2.70 | 0.007 ** | T_{r} | 298.2 | 83.6 | 3.57 | <0.001 *** |

T_{rp} | 79.9 | 36.8 | 2.17 | 0.031 * | T_{rp} | 191.4 | 94.4 | 2.03 | 0.044 * |

H_{2014} | 11.9 | 3.1 | 3.78 | <0.001 *** | H_{2014} | 48.5 | 8.1 | 6.02 | <0.001 *** |

T_{pr} : H_{2014} | −8.1 | 6.1 | −1.32 | 0.190 | T_{pr} : H_{2014} | −2.7 | 15.7 | −0.17 | 0.862 |

T_{r} : H_{2014} | −9.9 | 3.4 | −2.96 | 0.004 ** | T_{r} : H_{2014} | −25.1 | 8.6 | −2.91 | 0.004 ** |

T_{rp} : H_{2014} | −15.1 | 4.3 | −3.51 | <0.001 *** | T_{rp} : H_{2014} | −12.2 | 11.0 | −1.11 | 0.269 |

Ring 2015 | Ring 2016 | ||||||||

Estimate | Std. Error | T-Value | p-Value | Estimate | Std. Error | T-Value | p-Value | ||

(Intercept) | 197.1 | 21.9 | 9.02 | <0.001 *** | (Intercept) | 246.2 | 72.2 | 3.41 | <0.001 *** |

W | 93.7 | 26.3 | 3.56 | <0.001 *** | W | 194.3 | 97.4 | 2.00 | 0.048 * |

T_{pr} | 108.7 | 37.5 | 2.90 | 0.004 ** | T_{pr} | 324.3 | 162.5 | 2.00 | 0.047 * |

T_{r} | 35.8 | 25.6 | 1.40 | 0.163 | T_{r} | 586.3 | 119.6 | 4.90 | <0.001 *** |

T_{rp} | 34.7 | 26.6 | 1.31 | 0.193 | T_{rp} | −38.1 | 115.6 | −0.33 | 0.742 |

RGR_{2015} | 62.0 | 8.9 | 6.98 | <0.001 *** | RGR_{2016} | 127.5 | 29.7 | 4.30 | <0.001 *** |

W : T_{pr} | 203.6 | 198.9 | 1.02 | 0.307 | |||||

W : T_{r} | −85.7 | 134.1 | −0.64 | 0.524 | |||||

W : T_{rp} | 401.6 | 146.1 | 2.75 | 0.007 ** | |||||

T_{pr} : RGR_{2016} | 43.1 | 76.5 | 0.56 | 0.574 | |||||

T_{r} : RGR_{2016} | −112.9 | 44.1 | −2.56 | 0.011 * | |||||

T_{rp} : RGR_{2016} | 28.5 | 44.9 | 0.63 | 0.527 |

**Table 3.**Model statistics for the response variable latewood vessel diameter. The standard level of the categorical variable taxon of the mother tree (T) was Q. petraea, to which the other taxa were compared with. T

_{pr}: long stalked intermediate form, T

_{r}: Q. robur, T

_{rp}: short-stalked intermediate form. H

_{2014}: height at the end of the first growing season. RGR

_{2015}and RGR

_{2016}: relative growth rates in height for 2015 and 2016, respectively. W: adjusted relative extractable water in 2014.

Ring 2014 | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|

Estimate | Std. Error | df | T-Value | p-Value | |||||||

(Intercept) | 13.89 | 0.74 | 5041 | 18.79 | <0.001 *** | ||||||

H_{2014} | 0.58 | 0.09 | 201 | 6.58 | <0.001 *** | ||||||

T_{pr} | 3.16 | 1.59 | 201 | 1.99 | 0.048 * | ||||||

T_{r} | 1.95 | 0.91 | 201 | 2.15 | 0.033 * | ||||||

T_{rp} | 1.33 | 1.03 | 201 | 1.29 | 0.197 | ||||||

T_{pr} : H_{2014} | −0.47 | 0.17 | 201 | −2.73 | 0.007 ** | ||||||

T_{r} : H_{2014} | −0.36 | 0.09 | 201 | −3.81 | <0.001 *** | ||||||

T_{rp} : H_{2014} | −0.23 | 0.12 | 201 | −1.94 | 0.054 | ||||||

Ring 2015 | Ring 2016 | ||||||||||

Estimate | Std. Error | df | T-Value | p-Value | Estimate | Std. Error | df | T-Value | p-Value | ||

(Intercept) | 28.81 | 0.71 | 5041 | 40.56 | <0.001 *** | (Intercept) | 34.24 | 0.81 | 4896 | 42.12 | <0.001 *** |

RGR_{2015} | −0.55 | 0.29 | 203 | −1.91 | 0.057 | ||||||

W | 3.07 | 0.86 | 203 | 3.57 | <0.001 *** | W | 3.99 | 0.99 | 199 | 4.01 | <0.001 *** |

T_{pr} | 1.25 | 1.22 | 203 | 1.03 | 0.306 | T_{pr} | 3.30 | 1.40 | 199 | 2.36 | 0.019 * |

T_{r} | 2.43 | 0.83 | 203 | 2.92 | 0.004 ** | T_{r} | 2.72 | 0.97 | 199 | 2.79 | 0.006 ** |

T_{rp} | −0.10 | 0.87 | 203 | −0.12 | 0.742 | T_{rp} | 0.43 | 1.00 | 199 | 0.43 | 0.671 |

**Table 4.**Number of seedlings showing an intra-annual density fluctuation in the secondary xylem, depending on the water limiting treatment experienced by the seedlings in 2014.

Growing Season | n of Plants with Extra Ring | |
---|---|---|

Control | Drought | |

2014 | 5 | 23 |

2015 | 2 | 1 |

2016 | 2 | 1 |

**Table 5.**Statistics from the logistic regression model with the absence/presence of an intra-annual density fluctuation in the secondary xylem of the first growing season as response variable. W: adjusted relative extractable water in 2014.

Estimate | Std. Error | Z-Value | p-Value | |
---|---|---|---|---|

(Intercept) | −1.49 | 0.25 | −5.93 | <0.001 *** |

W | −1.64 | 0.61 | −2.70 | 0.007 ** |

**Table 6.**Statistics from the logistic regression models with the absence/presence of dendritic patterns (flame-like structures of grouped latewood vessels) in the secondary xylem in 2015 and 2016 as response variables. The standard level of the categorical variable taxon of the mother tree (T) was Q. petraea, to which the other taxa were compared with. T

_{pr}: long stalked intermediate form, T

_{r}: Q. robur, T

_{rp}: short-stalked intermediate form. RGR

_{2015}and RGR

_{2016}: relative growth rate of height in 2015 and 2016, respectively.

Ring 2015 | Ring 2016 | ||||||||
---|---|---|---|---|---|---|---|---|---|

Estimate | Std. Error | Z-Value | p-Value | Estimate | Std. Error | Z-Value | p-Value | ||

(Intercept) | −0.51 | 0.28 | −1.82 | 0.069 | (Intercept) | −1.10 | 0.78 | −1.41 | 0.159 |

W | −2.15 | 1.27 | −1.70 | 0.089 | |||||

T_{pr} | 1.71 | 0.68 | 2.51 | 0.012 * | T_{pr} | −0.12 | 1.82 | −0.07 | 0.946 |

T_{r} | 1.21 | 0.39 | 3.15 | 0.002 ** | T_{r} | −0.17 | 1.67 | −0.11 | 0.917 |

T_{rp} | 1.20 | 0.40 | 2.98 | 0.003 ** | T_{rp} | −3.22 | 1.19 | −2.71 | 0.007 ** |

RGR_{2015} | 0.46 | 0.22 | 2.15 | 0.032 * | RGR_{2016} | 3.86 | 0.92 | 4.19 | <0.001 *** |

W : T_{pr} | 14.54 | 41.58 | 0.35 | 0.727 | |||||

W : T_{r} | 6.83 | 6.57 | 1.04 | 0.299 | |||||

W : T_{rp} | 5.54 | 2.04 | 2.72 | 0.006** |

**Table 7.**Statistics from the cumulative logistic regression models with the level of vessel ring closure at the onset of the earlywood in the second and third growing season as response variables. The standard level of the categorical variable taxon of the mother tree (T) was Q. petraea, to which the other taxa were compared with. T

_{pr}: long stalked intermediate form, T

_{r}: Q. robur, T

_{rp}: short-stalked intermediate form. RGR

_{2015}: relative growth rate in height in the second growing season. W: adjusted relative extractable water in 2014.

Ring 2015 | Ring 2016 | ||||||||
---|---|---|---|---|---|---|---|---|---|

Estimate | Std. Error | Z-Value | p-Value | Estimate | Std. Error | Z-Value | p-Value | ||

W | 0.15 | 0.44 | 0.35 | 0.727 | |||||

T_{pr} | −0.61 | 0.46 | −1.35 | 0.177 | T_{pr} | −1.61 | 0.46 | −3.46 | <0.001 *** |

T_{r} | −1.64 | 0.34 | −4.80 | <0.001 *** | T_{r} | −1.55 | 0.33 | −4.78 | <0.001 *** |

T_{rp} | −1.28 | 0.34 | −3.80 | <0.001 *** | T_{rp} | −1.75 | 0.35 | −5.05 | <0.001 *** |

RGR_{2015} | −1.12 | 0.26 | −4.41 | <0.001 *** | |||||

W : RGR_{2015} | 1.06 | 0.31 | 3.43 | <0.001 *** |

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Vander Mijnsbrugge, K.; Turcsán, A.; Erdélyi, É.; Beeckman, H.
Drought Treated Seedlings of *Quercus petraea* (Matt.) Liebl., *Q. robur* L. and Their Morphological Intermediates Show Differential Radial Growth and Wood Anatomical Traits. *Forests* **2020**, *11*, 250.
https://doi.org/10.3390/f11020250

**AMA Style**

Vander Mijnsbrugge K, Turcsán A, Erdélyi É, Beeckman H.
Drought Treated Seedlings of *Quercus petraea* (Matt.) Liebl., *Q. robur* L. and Their Morphological Intermediates Show Differential Radial Growth and Wood Anatomical Traits. *Forests*. 2020; 11(2):250.
https://doi.org/10.3390/f11020250

**Chicago/Turabian Style**

Vander Mijnsbrugge, Kristine, Arion Turcsán, Éva Erdélyi, and Hans Beeckman.
2020. "Drought Treated Seedlings of *Quercus petraea* (Matt.) Liebl., *Q. robur* L. and Their Morphological Intermediates Show Differential Radial Growth and Wood Anatomical Traits" *Forests* 11, no. 2: 250.
https://doi.org/10.3390/f11020250